The psychology of Herbert William Mullin who murdered 13 people in southern California in the early 1970s but claimed his victims were sacrificed to save the lives of others. The programme explores how investigators brought an end to his crimes and experts discuss what might have driven him to kill. There is also an interview with Mullin himself. Last in the series., Serial Killing Saviour: Born to Kill. To Kill? Series profiling infamous serial killers. Was the heinous serial killer Herbert William Mullin driven by nature or nurture? Featuring a unique interview with the murderer himself.